Protein interactions are key determinants of protein function in biological systems. Despite the potential that quantitative protein interaction information could have for all areas of cancer research, unbiased or large-scale quantitation of protein interactions within native living systems is a challenge that is unmet by today's technology. The capacity to identify and quantitate protein interactions on a large-scale within native cells, patient samples, or tissues does not currently exist. Improved capabilities to quantitate protein interactions will have a major impact on the understanding of cancer, metastasis and the development of anti-cancer drug resistance. This project aims to develop and apply quantitative cross-linking with cancer cells with advanced Protein Interaction Reporter (PIR) technology. Stable Isotope Label of Amino acids in Cell culture (SILAC) will be combined with PIR technology to allow quantitation of protein levels and protein interactions in cells. These capabilities will be applied to cisplatin-, taxol-, and SN-38 resistant cancer cells to allow quantitation of interactions relative to drug sensitive cancer cells. This project will provide the first relative quantitation data on protein interactions in cancer cells and the first unbiased measurements of functional regulation at the protein interaction level relevant to drug resistance.